Drogues

[Roger Long]

The subject of drogues keeps coming up in the threads about heavy weather. Certainly, they are essential equipment for any boat going offshore for longer periods than weather forecasts can be relied upon.

I'm a big fan of the Series Drogue. Everything I know and can infer about waves and the behavior of vessels tells me that it is the cat's pajamas. I found the research and rational behind it quite compelling when read it. I may equip my boat with something else when the time comes however.

If drogues were one of those things we used constantly and switched models from time to time so we could compare, I have no doubt the series drogue would be Editor's choice every time. "Best" is sometimes just a small increment on top of "sufficient" however. Since many have gotten all the way around the world without needing a drogue I might choose something simpler and cheaper.

If you were to do an evaluation of drogues based on equal overall drag and total overall length, I think a graph of effectiveness, easy of control and depoyment, and other "goodness" factors would look something like what is shown below. Single drogues have worked as have milk crates and other stuff tied on to an anchor rode. Water moves back and forth in various parts of a wave so spreading the drag out so that the pull is an average of surface water motion behind the boat, instead of just an anchor at one point in it is, essential. However, I think there is probably a point of diminishing returns.

The Series Drogue would be way off to the right in the graph and clearly superior but, by how much? I might well opt for 6 - 8 small cone sea anchors that I could tie into an anchor rode with the line running through the holes in the cone ends. It would stow more compactly and probably be something I could make myself more cheaply.

Spreading 6 - 8 small cones out over the same distance ought to achieve fairly similar results. I would be very interested though in any actual drogue use accounts that might challenge this proposition.

 

[newly anonymous]

coast guard report

Have you seen this, Roger?
http://www.seriesdrogue.com/coastguardreport/

They tested one series with 90 cones attached. Graphed out pretty much like yours.

The advantage I see to such a system over a parachute-type sea anchor is twofold: first, it won't wobble as much, meaning less chafe; second, it will be far less difficult to get back onto the boat after deployment.

Would love to see one designed that uses existing rode. Begin by towing a warp attached to each stern cleat, and add the series drogues via a snatch block. The warp then acts as a giant towing bridle.

 

[Roger Long]

Have you seen this, Roger?
http://www.seriesdrogue.com/coastguardreport/

The advantage I see to such a system over a parachute-type sea anchor ....

Yes, that was part of the first things I read when I first heard about this style of drogue.

This has all been extensively discussed here and elsewhere but I'll sumarize:

The advantage over a parachute downwind is that you can use it at all. A parachute is essentially fixed in the water. Think about being anchored in big waves. Would you want to do that by the stern? Parachutes have their place but it is generally as a substitute for a ground anchor in conditions where anchoring to the ground would be at least survivable. They are not survival storm gear but for use when the crew needs to get rest, the boat needs to remain in a somewhat confined geographical area, and waves are not large enough to present a roll over hazard.

When sea room is sufficient and the waves are large enough that going downwind with some speed to reduce the force of crest impact is the best option, a drogue will usually be essential to maintain control except in the case of craft with large crews that can rotate fresh experienced helmsmen frequently. It has to be small enough to drag through the water and allow some headway.

A single smaller cone will work and has often been used successfully. However, water moves forward and back as waves go by and the crest lengths are not always consistent. If the single drogue is moving forward at the wrong moment, your boat may be deprived of steadying force just when it most needs it. The boat surging forward on a wave as the drogue is pulled back can exert enormous strains.

The beauty of the Series Drogue is averaging the pull over several wave crests as well as having the trailing weight pulling much of it below the fore and aft surge of the surface waters.

My point is simply that 6 - 8 cones spread over the same length of rope will probably do this nearly as well as 20 - 30 and be easier to store and fabricate. They won't do it as well but I would expect it to be good enough.

 

[tsmwebb]

What cost safety?

The subject of drogues keeps coming up in the threads about heavy weather. Certainly, they are essential equipment for any boat going offshore for longer periods than weather forecasts can be relied upon.

[emphasis added]

I know one person who thinks he was saved by his para-anchor. He was caught in a gale in his 10 meter catamaran between New Cal and Oz. And, in the interest of full disclosure, I carry a para-anchor and a single cone style drogue on my boat. And, I even set my drogue during a frontal passage between New Zealand and Tonga as an experiment and it worked pretty well. However, I wonder if a drogue is really essential equipment for an offshore cruising yacht. They are certainly desirable if you have the funds, space and payload for them. However, if I had to choose between good rain gear and a drogue, the foulies would win out every time. Drag devices are very rarely used by yachts traveling in season at reasonable latitudes. Mostly they inhabit sail lockers and are ignored as they get moldy and weak. As I say, I carry two drag devices, but I think of them in the same way as I think of a nice bottle of scotch. I can afford them and they make me feel good, so why not? But, I'd go offshore without them without hesitation.

--Tom.

 

[Roger Long]

[emphasis added]I know one person who thinks he was saved by his para-anchor. However, I wonder if a drogue is really essential equipment for an offshore cruising yacht.

Multihull dynamics are different and my impression is that I've heard more favorable reports about para-anchors on those craft. Multihulls are pretty far off my radar screen though.

There are offshore routes and seasons when I would go without a drogue as well. I think that's covered by the weather forecast part of my post. There are places where you can count on no major weather for a month or so. I wouldn't want to be out with any signifcant chance of conditions severe enough that being rolled was possible without a drogue though. It's like a liferaft. You hope you never get your money's worth or maybe you use it just once.

 

[Franklin]

I agree. I have two dragging devices. One is a drifter for fishermen that I got for just $25. I used it once hoping it would keep my boat stable and point the bow into the waves as there were 3' waves and only 3 knots of wind (very rocky). It didn't work as there just wasn't enough movement of the boat to give it bite. I figure I'll use it in medium conditions where I just don't feel like beating into the waves and just want to wait it out...or in waters shallower then 300'.

I also have the Jordan Series Drogue which is the beast that is supposed to safely control my boat in any heavy weather (maker even claims it works in hurricanes). I don't think I will ever need it until I cross an ocean, but I will always have it with me.

Now both of these are so I can drop the sails and tie off the helm and go below. There are others that you want to use that just keeps the boat under control while you are still at the helm.

I know of one sailor who survived many storms in 30 years of singlehanded offshore racing and all he ever used was warps. Now the boats he sailed on were the old types from the 20s to 60s so they aren't like we are using today, but he claims he could throw out his warps and tie off his tiller a certain way and it would drift with waves on his rear quarter.

He did say though that he was pooped (a true filling of the cockpit) twice and both times it was at the end of storms and caused structural damage on both boats. The Jordan Series Drogue maker claims you will never be pooped on.

So I think it's wise to have different things you can deploy to fit the situation and what you plan on doing.

 

[Ross]

In the book Storm Tactics Larry Pardey discusses the many methods used for weathering severe weather and the ways to heave-to in different boats. I gather from that (and I have no off shore experience) book that what works very well for one configuration boat may not serve well in a different boat. The recommendation seems to be to try different methods in moderate storm conditions until you find a system that works well in your boat with your crew. Am I missing something in there or is that a reasonable approach. I get the impression that adequate sea-room is of paramount importance.

 

[Franklin]

A Jordan Series Drogue will stop a boat just as much as a sea anchor. It is a "drop sails, tie of the helm and go below" device. Mine has 115 cones and 300' of line for a 9 ton boat. They will tell you how many cones you need for the weight of your boat.

It is not a device you drag and sail with.

There are tons of reasons why you would want to use it instead of a sea anchor and I will try to list some of them here:

1) when you want to deploy something like this, 9 times out of 10, you are already running with the wind, so it's a much better idea to deploy something off the stern then the bow in that situation.

2) because it's 300' long, a wave can't get ahold of it and throw it.

3) when anchored off the bow, you swing on anchor because of the mast being forward of the keel and other design problems, but not when you are anchored from the stern (this I have definately proven).

4) numerous rudders have been broken under sea anchor because you are drifting backwards and you are swinging at anchor. Going backwards is hard on rudders, but the additional stress caused by the swing in such strong winds is too much.

I'm sure there are more reasons but I can't think of them now.

 

[Roger Long]

Am I missing something in there or is that a reasonable approach?

Completely reasonable. Being able to predict your vessel's behavior is a vital component of competence. Look what happened to your friend when he didn't know that his boat wouldn't just magically lie to the sea anchor (most won't). He was probably in more danger from the gear and the line running out than the weather.

However, sea conditions and situations vary so much that developing a rigid strategy is probably not a constructive goal. The experience and confidence gained working in stressfull conditions and learning how to handle the gear may be a larger contributor to safety.

Something that isn't discussed often enough about bow deployment of drogues is the effect on rudders. The Pardy's are major proponents of sea anchors on bridles but they also sail a type of vessel that tends to have a massive rudder and tiller. A friend from Clear Lake lost his 40 foot steel ketch just a year ago due to steering gear failure surging backwards with a 12 foot para-drogue deployed Pardey style. They had other problems which restricted their options but the boat was doomed by a piece of the broken steering gear piercing the hull.

 

[Franklin]

I gather from that (and I have no off shore experience) book that what works very well for one configuration boat may not serve well in a different boat.

Very true. It is much easier to get a full keel boat to do a PROPER heave-to then a light weight fin keel boat. Fin keel boats want to sail and it's very hard to stop them going forward. You can backwind the jib just as easy and slow the boat down to 1.5 knots just as easy, but to get the drift to be sideways instead of forward is the hard part. That sideways drift is what gives a heave-to it's safety in seas. The disturbance producted by the keel is supposed to prevent waves from breaking. If you can't get a sideways drift, that distrubance isn't going to hit the wave before it hits you.

IMHO, I also believe that the real dangerous seas are in winds where you've already have taken down all your sails and are running bare poles. I don't see anybody putting the sails back up to heave-to once they are in those conditions. Now maybe in boats that don't have to reef until 25 knots but I have limited experince on those kinds of boats.

 

[Roger Long]

It (Jordan Series Drogue) is not a device you drag and sail with.

Quite right. It's for use when sails are struck and you need to be below for personal safety. However, there will be some forward headway. The reason they want to size it to your boat is to attempt to get the forward speed into an optimum range. The claim that you won't get pooped is based partly on the fact that the boat is not fixed in position. I take that claim with a grain of salt though.

I'd forgotten they have so many cones. I still think most of the effect, although not the ease of handling, would be acheived with fewer cones. I would trade off the ease of handling for having something I could assemble on a length of rope available for other purposes.

 

[tsmwebb]

There are offshore routes and seasons when I would go without a drogue as well. I think that's covered by the weather forecast part of my post. There are places where you can count on no major weather for a month or so. I wouldn't want to be out with any signifcant chance of conditions severe enough that being rolled was possible without a drogue though. It's like a liferaft. You hope you never get your money's worth or maybe you use it just once.

Fair enough. It's largely a matter of taste. For some folks a Smart Car is a deathtrap and others are happy astride a Ninja... Comfort levels can't be explained by risk analysis. I can't think of any passages that I've taken that I would not have taken if I had to give up my drogue and para-anchor. But then again, I carried them along so there you go ...

You get big time bonus points from me for being willing to admit that you're not a multihull expert. Bet that's worth a bunch . When we were up in San Francisco I was browsing sailing books at a book store and saw a cruising how-to by a sailing couple that I've met and who I think have their heads on right way. Being a multi-guy now I turned to the multihull discussion. It was a full chapter, the first line of which was (and I paraphrase) "We don't have any multihull experience and only have one friend who does. So, here's all you need to know about multihulls..." Why couldn't they have stopped with we don't know and suggested looking for an authority? I've also seen a book by an expert who took the righting curve for a multi, scaled it to fit under the curve of a monohull and then proceeded to use that bogus illustration as the starting point for his discussion of multis... :neutral: This is one reason why many multi types have "issues" with the mono world.

Woops, sorry for that vent. Now back to our regularly scheduled thread...

--Tom.

 

[Franklin]

... I still think most of the effect, although not the ease of handling, would be acheived with fewer cones. ...

Nope. The number one goal of the Jordan Series Drogue is to prohibit a boat from sliding down a very large breaking wave. If you are on a 40' breaking wave, the water that breaks will slide down the wave and the boat will not have any traction. It takes all 115 cones to stop the boat from sliding down the wave and crashing into the trouph. They have an excellant description on their website on how a 50' boat was crushed in the trouph and how a Jordan Series Drogue would have prevented it.

 

[Ross]

Fair enough. It's largely a matter of taste. For some folks a Smart Car is a deathtrap and others are happy astride a Ninja... Comfort levels can't be explained by risk analysis. I can't think of any passages that I've taken that I would not have taken if I had to give up my drogue and para-anchor. But then again, I carried them along so there you go ...

You get big time bonus points from me for being willing to admit that you're not a multihull expert. Bet that's worth a bunch . When we were up in San Francisco I was browsing sailing books at a book store and saw a cruising how-to by a sailing couple that I've met and who I think have their heads on right way. Being a multi-guy now I turned to the multihull discussion. It was a full chapter, the first line of which was (and I paraphrase) "We don't have any multihull experience and only have one friend who does. So, here's all you need to know about multihulls..." Why couldn't they have stopped with we don't know and suggested looking for an authority? I've also seen a book by an expert who took the righting curve for a multi, scaled it to fit under the curve of a monohull and then proceeded to use that bogus illustration as the starting point for his discussion of multis... :neutral: This is one reason why many multi types have "issues" with the mono world.

Woops, sorry for that vent. Now back to our regularly scheduled thread...

--Tom.

Do Proas qualify as multihulls?

 

[tsmwebb]

The recommendation seems to be to try different methods in moderate storm conditions ...

Yes, experiment in a stiff breeze or near gale conditions. Make an effort to avoid the "moderate" storms

--Tom.

 

[tsmwebb]

Do Proas qualify as multihulls?

Yes, and I've sailed one in protected water and that's all I know about that

--Tom.

 

[Roger Long]

It takes all 115 cones to stop the boat from sliding down the wave and crashing into the trouph.

It takes 115 cones because they are little cones. I'm thinking about the same amount of drag and same general geometry but with the distributed drag broken up into fewer and larger units. The real key is to make sure that all the drag units don't wind up in the same wave half which might be surging the same direction as your boat.

I was talking about 6-8 vs. 20-30 above but that was just memory failure. I should have said 20 - 30 vs the hundred or so they apparently have. It's still a more managable number if you want something you can make up when needed. I have no doubt that more is better for ultimate performance but I question how much better it is.

BTW it reminds me of a story I heard once about another single handed grandmother (other than Donna Lange). She was struck by a gale so she threw a single large cone sea anchor over the stern on a short rope and went back to her knitting, arriving in Ireland in due course. Putting the single drogue on a short rope may have made sense because it made sure that it was in pretty much the same part of the wave as the boat.

 

[tsmwebb]

Putting the single drogue on a short rope may have made sense because it made sure that it was in pretty much the same part of the wave as the boat.

Hmmm, is that a good thing? What happens if the boat and anchor are both in a wave trough? Will the anchor help prevent a broach?

--Tom.

 

[Franklin]

The advantage of making the cone small is that they don't need to be very strong. Each cone only grabs a little water, but with so many on one line, that one line creates a great drag.

It is very easy to make your own. There isn't any special material used.

 

[Roger Long]

The advantage of making the cone small is that they don't need to be very strong. Each cone only grabs a little water, but with so many on one line, that one line creates a great drag.

Agreed. It's a great concept. I just went back and re-read their web site. My boat would have about 105 cones on a 175 foot line. The drag coefficient of cones should be pretty similar over this size range so equal swept area should give pretty similar drag. If I used 10 cones, they would be 16" diameter, which is a workable size, and spaced 17.5 feet apart on the same 175 foot line and 75 foot leader.

It's hard to see that 10 cones at 17.5 foot intervals are going to behave significantly differently than 105 at about 18" intervals. I would rather handle and deploy the standard design Jordan. However, in view of the fact that I very likely would never use it, I'd like to have all that rope available for other emergency purposes and space is limited on a 32 foot boat. Attaching 10 cones is a lot more practical before a storm or a passage than attaching 105.

If you have the room for it, and are going to have a lot of major storm exposure, the Jordan is certainly the way to go and I expect it's deployed performance is slightly better. I think a 10 cone design makes sense in my circumstances though.